1. Field of the Invention
The invention relates to generating clock signals and synchronizing data signals with a generated clock signal. More particularly, the invention concerns processing a reference frequency signal to generate a plurality of clock signals, and synchronizing data signals with one of the generated clock signals.
2. Description of the Related Art
Code division multiple access (CDMA) cellular radiotelephone networks are a widely used type of spread spectrum communication system. Frequently, mobile telephones are small handheld units operating from battery power. Consequently, power conservation is a constant goal of handheld radiotelephone designers. A well known technique for saving power entails reducing the clock rate or completely cutting off the clock supplied to components of the radiotelephone that are not needed for the present mode of operation of the telephone. When the clock to selected components is reduced or eliminated, the telephone is in what is referred to as a secondary mode of operation.
For a CDMA radio telephone system to operate correctly, it is necessary for the radiotelephone to have a master timer that establishes and maintains synchronism with a CDMA network timer. To enable the radiotelephone to resume communications with a base station quickly and without using an excessive amount of power after leaving the secondary mode, the radiotelephone must maintain synchronism with the network timer even when the radiotelephone is in the secondary mode.
Typically, a radiotelephone has an analog transceiver that is commonly left operating when the radiotelephone is in the secondary mode, because the radiotelephone provides timing signals. However, leaving the analog transceiver operating during the secondary mode increases power consumption during the secondary mode due to the power consumption of the analog transceiver.
Consequently, there is a need for a way to maintain CDMA network time in a radiotelephone while the radiotelephone is in the secondary mode, without running the analog transceiver. Additionally, it would be desirable to clock a digital transceiver in a radiotelephone at a frequency higher than the commonly used frequency of chiprate(8), in order to allow for more efficient usage of digital transceiver resources through timesharing.